Stator having three-phase superconducting windings

Abstract

An electric machine stator (6) having superconducting three-phase windings, the stator comprising tubular elements (7, 8) and end plates (9, 10) forming a cryogenic enclosure containing a bath of liquid helium at very low temperature, with the windings being disposed in said bath, an additional tubular element (11) supporting said enclosure at one of its ends and fixed at its other end in sealed manner to an additional end plate (3), annular screens (13, 14) for reflecting radial thermal radiation, and current leads to the windings, the stator including the improvements whereby the tubular elements and the end plates forming the enclosure, the tubular element supporting the enclosure, and the annular screens for reflecting radial thermal radiation are based on a material which does not conduct electricity, and whereby the annular screens for reflecting radial thermal radiation are covered with layers (41, 43) of metal wires of high thermal conductivity, each of which layers has at least one point thereof put into heat conducting connection with a heat exchanger having a chamber (16) through which flows gaseous helium evacuated from the enclosure passing therethrough.

We claim: 
     
       1. In an electric machine stator including superconducting three-phase windings, said stator comprising tubular elements and end plates forming a cryogenic enclosure containing a bath of liquid helium at very low temperature, said windings being disposed in said bath, an additional tubular element supporting said enclosure at one of its ends and fixed, at its other end, in a sealed manner to an additional end plate, annular screens for reflecting radial thermal radiation, and current least to the windings, the improvement wherein the tubular element and the end plates forming the enclosure, and the annular screens for reflecting radial thermal radiation are formed of a material which does not conduct electricity, and wherein the annular screens for reflecting radial thermal radiation are covered with layers of metal wires of high thermal conductivity, each of which layers having at least one point thereof forming a heat conducting connection with a heat exchanger having a chamber and means for passing a flow of gaseous helium evacuated from the enclosure through said heat exchanger chamber. 
     
     
       2. A stator according to claim 1, wherein the tubular element for supporting the enclosure and the annular screens for reflecting radial thermal radiation are made of a glass fiber and resin composite material. 
     
     
       3. A stator according to claim 1, wherein the heat conducting connection between a point of an inner annular screen for reflecting radial thermal radiation and the heat exchanger having the gaseous helium flow chamber is constituted by a braid of wires made of a metal which is a good conductor of heat. 
     
     
       4. A stator according to claim 1, wherein the heat conducting connection between a point on the outer annular screen for reflecting radial thermal radiation and the heat exchanger having a chamber with a flow of gaseous helium is constituted by a metal junction member. 
     
     
       5. A stator according to claim 1, further including a braid of wires made of a metal which is a good conductor of heat providing a thermal connection between a point on the additional tubular element for supporting the enclosure and the heat exchanger having a chamber with the flow of gaseous helium. 
     
     
       6. A stator according to claim 1, wherein the heat exchanger comprises a ring of sintered conductive metal disposed in the heat exchanger chamber through which the gaseous helium evacuated from the enclosure is made to flow. 
     
     
       7. A stator according to claim 1, wherein the enclosure is supported at its end opposite to the end which is connected to the tubular supporting element by means of rods of stainless steel which are fixed to the cylinder which forms the outermost envelope. 
     
     
       8. A stator according to claim 7, wherein the rods of stainless steel are in three groups of rods disposed at 120° intervals. 
     
     
       9. A stator according to claim 1, further including a box connected to the current leads through which very low temperature helium flows, and said box being provided with disks of sintered conductive metal having passages passing therethrough for the current leads. 
     
     
       10. A stator according to claim 1, wherein the current leads are made of a normally conductive metal and said current leads are wound around a helically machined tube having a helical wall which tube is contained in a coaxial outer tube of slightly larger diameter than the outer diameter of the machined tube, and wherein said helical wall delimits a helical outlet path for the very low temperature helium which is in contact with the current leads. 
     
     
       11. A stator according to claim 1, wherein the current leads are made of a metal exhibiting normal conductivity. 
     
     
       12. A stator according to claim 1, wherein the current leads are made of a superconducting material.